An observer A and a charge Q are fixed in a stationary frame F. Another observer B is fixed in a frame f, which is moving wrt to F. then

An observer A and a charge Q are fixed in a stationary frame F. Another observer B is fixed in a frame f, which is moving wrt to F. then?

a) both A and B will observe electric fields.
b) both A and B will observe magnetic fields
c) neither A nor B will observe magnetic fields
d) B will observe a magnetic field, but A will not